Trying to help a friend’s mindset.

So my roommate and I play league not always together and when he is alone playing he gets very toxic without typing in chat. Just saying stuff like “My Laners feed everytime I play a game.” I was generally curious cause he is good in my eyes for a silver 2 player and should be able to easily hit gold but I needed to see his game. I had him sit down with me and we watched a replay and saw several errors in his play and like if thinking that I don’t agree with. Like staying in lane after getting a kill and using mechanics over item advantage. We went through the whole game and still tried to blame everyone else on the team even though ultimately he lost the game for his team. He then said “I can’t take anything you say seriously I don’t know why.” And stormed out of the room. I can’t figure out how to get him to over this stereotypical zed/yasuo/riven mindset.